A system for presence monitoring and in particular for presence monitoring in multiple presence buildings, so that emergency services can get an accurate presence list in the case of an emergency. A mobile device belonging to a user outputs a location notification to a location module when it crosses a geofence defining the boundaries of a facility. The location module monitors the location of one or more mobile devices belonging to users and outputs an indication whenever a location notification is received. A register module then operates in response to the location module to generate an up to date presence list for the facility based on the identity of monitored devices within the geofence. An interface outputs the presence list on demand and can transmit the presence list to one or more external devices or locations in response to an evacuation alarm.